The Seattle sound had been developing for the latter half of the 80's. Bands like Green River, Mudhoney and Soundgarden and so on. Soundgarden's "Badmotorfinger" was released in 1991 as well. The quintessential album of the 90's, IMO was Temple of the Dog, and it was released in 1990.

Pearl Jam was created from the bones of Green River and Mother Love Bone. While I believe that Pearl Jam ecompasses all that is early 90's "Grunge", Nirvana didn't start the trend.

Again, I fully disagree. And as far as "paying attention", you couldn't be further from the truth, especially since I began working for Uni in 1993.

MBL is more of an LA metal sound than Seattle Grunge. Mudhoney was indeed a pioneer, as was TotD, but the sound first emerged on SG's 'Louder than Love' in 1990.

However, until the first showing of Teen Spirit on MTV, those acts were music geeks' little secrets. So Nirvana 'started the era' in the sense of authoritatively announcing its arrival and dominance for the next 5 years. A week before, Guns 'n' Roses were undisputed and deserved cocks of the walk.